Silver halide emulsions sensitized by mixtures of high polyalkylene glycols and low polyhydric alcohols



fizz-tented May 11 1948 UNITED. sures HOLS 7 Ralph Kingsley Blake,

Rochester, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., 2. corporationoi pelaware I No Drawing.

This invention relates to photography and, moreparticularly, to radiation-sensitive photographic elements sensitized by means of a mixture of a olyglycol of high molecular weight and a low monohydric alcohol, dihydric alcohol, or a monoalkyl ether thereof, of not more than 2 to 6 carbon atoms. Still more particularlyit'relates to suchelements sensitized'by meansfof a mixture of a polyglycol having a molecular weight I of at least i 1bii e ji91 are te ra alkoxy compounds.wamlmmi illma qlwk lwxii 4 compounds. Other objects will be apparent from the following description ofithe invention.

It has been discovered that the speed and/or efiective contrast of photographic silver: halidecoloid emulsions and emulsion layers can be increased by bringingthem into operative associationorv contactwith a mixture of a smallamount of (a) a polyglycol having a molecular weight of at least 400, and (b) a saturated, aliphatic polyhy-dric alcohol of 2 to 6 carbon atoms and their alkyl ethers and fatty acid esters containing not more than 3 -carbon,atomsjinjhe etlierpr ester radical. Thus, the methyL ethylg and isopropyl ethers and the acetic andproplonic acid; esters maybeused. f f;- f

The mixtures of compounds described above can be brought into operative association with the silver halide emulsion layer in various manners. This may be accomplished prior to coating of the emulsion layer or after the emulsion layer has been formed. The latter situation may be accomplished byimpregnatingpr-coating a colloid silver halide emulslon'l-ayer-with asolution containing theaforedescribed mixture LAI- ternatively the mixtures can be incerpor'atedynh a substratum coating or in an overcoatin'iwhich Specifically, an object of this and/or contrast'r Application becemher i1 2, 1946, V Serial No. 115,631; n v g 9 Claims. (01,, 95- 7) f A 2 is in operative association with the emulsion layer. 1 It, has been found that the use of the mixtures Iin uestiOn have a synergistic effect which is similargto thesupersensitizing action conferred by certain sensitizingdyes However, the novel combinations confer an increase in the total sensitivityiofthe emulsionratherthan in certain nar- 1rowfregions of the spectrum. The increase in se nsitivity'is beyond that obtained by the use lofjoffiithe indiVidualc nstituents of the mixture alone.

The polyglycols described above are known chemical compounds and many of them are available commercially. They can be prepared in various ways; for example, by the removal of water from glycols and by the reaction of oxides with glycols.-- The reactions-are generally carried out until theproducts have a molecular weight or an averagemolecular weight in excess of 400. Ethzoylene oxide, propylene oxide-1,2, and -1,3 and butylene oxides-4,2 can be used in the preparation of fth'e'products and they may be reacted with ethylene glycol or diethylene glycol. Their preparation is described in The Chemistry of 25 synthetieResins, pages 990-994, published by Rheinhold Publishing qorp. (i935) V f the invention involves :T 'rcie. e2 aspect tsensitizing silverhalide colloid emulsions or emulvlsion layers with 'a 'mixtureof (a) one or more momne eds ihe orm 7 nocnzcnzownscmm,lcnzcnzon (1) 'whereinjis'lsto 200 0r.,more and (b) a polyhydric alcohol of 2 to 6 carbon atoms and their alkyl 35 ethers and fatty acid-esters containing not more than 3 carbon atoms in the ether or ester radical. -Compoundshaving such a Formula 1 include nonaethylene glycolgdecaethylene glycol, dodeca- "BltHYlGliglycol and higher homologues contain- ":50 general; the higherimembers of: the series cannot 3 be too easily isolated as single chemical entities. N-methyl-p-aminophenol sulfate grams 2.5 Instead, the condensation reaction leading to Hydroquinone do 30 their preparation is carried to a point where the Sodium sulfite (anhydrous) do 750 bulk of the material will consist of homologous Borax do 5.0 compounds of similar chain length. Mixtures of 5 Water to 1iter 1.0 two or more polyalkylene glycols or polyoxyalkylene glycols are selected on the basis of average fiXed, Washed, and dried- The following results molecular weight. Since a diiference .of one or were obtained: two ethylene oxide links in polymers of consid- I erable chain length has a negligible effect on their P01 6th 19118 a physical and chemical properties, such mixtures i o1 001 Av. 'tive Gamma Fog can be readily employed in the present invention. y 0 7200 Speed For the purposes of this invention, it is sufiicient to know the average molecular weight of the 100 88 05 material to be used and the fact that it may in "5'0" 107 I80 I04 all likelihood consist of a mixture of several compounds of closely similar molecular weights does :0 100 I m not reduce its effectiveness.

It has been discovered that the aforedescribed 1 103 I 1 mixtures of high polyalkylene glycols and lower polyhydric alcohol compounds are capable of increasing the sensitivity of photographic emulsions equally throughout the whole range of th spec- Example H trum in a manner analogous to the so-called V u u S t ch as allylthiou eas, t The following results were obtained in exactly y es, Sodium thiqsulfate, and sodiu hyp the same manner as described in Example I ex- Sulfite, yfit y differ Widely ll cillnstitution and oept that the resulting film elements were develprflperties from Such po he D Y- oped for 7, 10, and 25 minutes in a developer of glycols, moreover, may be used in conjunction t formula; with such sulfur sensitizers and have a beneficial efiect 0n the resulting emulsion. N-methyl-p-aminophenol sulfate grams 0.735

The mixtures are especially effective with gel- Hydroquinone do 1.000 atino-silver halide emulsion layers but may be Sodium sulfite (anhydrousL do 90.400 used with any water-permeable binding agent for Borax do 2710 silver halides. These emulsions may contain Potassium bromide do 0.113 optical sensitizers which increase the sensitiv- Water to "liter" 1.000

Relative Ethylene Propylene 81 33 2? Speed Gamma Fog Glycol Glycol Mol. Wt. 7200+ 7' 10' 25' 7' I 10' 25' 7 0' 25' M. Mg. 7 .100 132 200 .33 .53 .81 .01 .01 .05 33.3 142 132 214 .55 .70 .31 .04 .05 .11 5.0 33.3 137 174 240 .53 .07 .93 .03 .05 .11 10.0 33.3 200 230 233 .57 .70 .07 .04 .05 .11 20.0 33.3 230 230 303 .00 .79 .03 .04 .05 .11 20.0 132 5 152 230 .45 .03 .35 .02 .01 .05 33.3 200 230 233 .59, .75 .93 .04 .05 .11 123 142 240 .47 .07 .34 .01 .01 .04

ity of silver halide emulsions preferentially to Example I A gelatino-silver halide emulsion containing 77% silver iodide and 92.3% silver bromide was brought to its maximum light-sensitivity in condition for pouring. The following quantities'ofethylene glycol and polyethylene glycol having an averagemoleeular weight of 7200 were added to the samples of the above-described emulsion each containing about 0.15 mol of silver halide. The

resulting emulsion samples were coated on cellu-' lose nitrate film base in a thin layer and driedin a manner known to the art. Samples of said film elements were then exposed in a type. IIB sensitometer, developed in a developer of the following composition for nine minutes at 69 F.:

' 175,- or E mnle I ExampZe III The following'results were obtained in the same 'manner as described in Example I except that the resulting filmelements were developed for ten minutes in a developer like that of Example II.

Diethyl- Polyethylene one Glyc v.

M01.Wt.7 200 Glycol Gamma Fog Example IV The following results were obtained in exactly the, same manner as described in, Example I exceptjthat the resultin lm elements were. developedflfor seven minutes in a developer like that age-molecular weight of 7200.

, ADiethylene Glycol.

B-Ethylene Glycol. C--Propylene Glycol.

D -Dipropylene Glycol. E -EthyleneGlycol Mono-Ethyl Ether.

F-Propylene Glycol-Av. M01. Wt. 7200.

Example V Q; following results were obtained in the same manner as described in Example I except that'the resulting film elements were developed .for -ten minutes in a developer like. that of Example II.

aggi Polyethylene Rem Ethylene G1ycl tive Gamma Fog Glycol Speed Acetate 1 T Example VI ""The following results were obtained' in" the same manner as described in Example I except that the gelatino-silver halide emulsion contained 6.8% silver iodide and 93.2% silver bromide and the resulting film elements were d veloped for seven minutes in a developer like that of Example II.

Z-Amlno- Polyethylene Rpla- .2-Methyl- G-lycolAv. tive Gamma Fog '1, B-Propanediol Mel. Wt. 7200 Speed Grams Mg. 100 176 .04 10.0 115 .70 .07 3. 33 142 73 07 3. 33 10.0 174 75 07 7 Example VII 1 To approximately 0:15 mol samples of a gelatino-silver halide emulsion containing 7.7% silver iodideand 92.3% silver bromide were added the following quantities of butanediol, trlmethylene glycol. andpolyethylene glycol having an averv The emulsions werethen brought to maximum light-sensitivity andprepared for coating. The resulting emulslon samples were coated on cellulose nitrate film base a thin-layer-and dried iii-a manner known to the art. Samples of said film elements were then exposed in a type 1113 sensitomet'er, developedvina developer like that in Example II for ten minutes at 68 F., fixed, washed, and dried. The following results were obtained:

Example VIII To approximately 0.15 mol samples of a gelat- -i'no-.-silver'halideemulsion containing 6.8% silver iodide and 93.2% silver bromide were added the following quantities of glycerine formal, glycerine, =di(beta-hydroxyethyl) formal and polyethylene glycol having an average molecular weight of 7200. The emulsions were then brought to maximum light-sensitivity and prepared for coating. The resulting emulsion samples were coated on cellulose nitrate filmbase in a thin layer and dried in a manner known to the art. Samples of said film elements were then exposed in a type 13 sensitometer, developed in a developer like that of Example II for seven minutes at 68 F., fixed, washed and dried. The

following results were obtained:

' The following results were obtained in the same manner as described in Example I except that the gelatino-silver halide emulsion contained 6.45% silver iodide and 93.55% silver bromide." The resulting film elements were exposed in a type IB sensitometer and develope'rafor seven: minutes inqa developer like that-101 Example 11. "1 5- Ethyl- Relaene K L M N tive Gamma Fog Glycol Speed lVIl. M1. M1. G G 111g.

100 .74 03 100 76 01 20 0. 67 132 82 03 0.67 123 .78 .05 2o 0.3a 152 .90 .03 0.33 123 .87 .08 20 I 100 .74 .04 20 33. 3 123 .70 .09 20 100 .76 06 33.3 115 .77 .09 20 1. 33. 3 132 .81 .07 20 100 .73 .05 33.3 115 .76 .08

N -Polyethylene GlycolAv. Mol. Wt.

assuage M Polyethylene Glycol-Av. M01. Wt. 550.

3600. O-Polyethylene Glycol-Av. M01. Wt. 7200.

Example X A dispersion of light-sensitive silver halide salts comprising 2.8% silver iodide and 97.2% silver bromide free of gelatin was prepared in a synthetic resin binding agent consisting of m-(lhydroxynaphthalene-2-sulfonamiclo) benzaldehyde polyvinyl acetal. This dispersion was brought to maximum light sensitivity and four samples, each containing 0.15 mol of silver halide,

taken therefrom. Polyethylene glycol having an average molecular weight of 7200 and ethylene glycol were then addedto these samples as indicated below. The dispersions were coated on heavy white baryta-coated paper and dried in warm, dry air. The samples were then exposed on asector-wheel IIB type sensitometer, developed for five minutes at 68 F. in a developer of the following formula:

N-methyl-p-amincphenol sulfate grams 2.0 Hydroquinone s; do' '60 Sodium sulfite' (anhydrous) do 50.0 Sodium carbonate do 28.3 Potassium bromide do 1.0 Citric acid do 2.0 Water to liter 1.0

E 3 Eth 1 t y ene y Glycol-Av. enc Total Density MoltWt. Glycol g My. Ml. .23 .31 .50 .85 1.40 1.62 .21 33. 3 1 22 38 63 1. 04 1. 44 1. 60 18 .22 .3l .48 .80 132 1.61 .19 33.3 20 .25 .43 .60 1.10 1.48 1.62 .10

As described in: the preceding examples, the

mixtures of the higher polyalkylen'e glycOls and lower polyhyd'ric. alcohols and theirethers and esters of the present invention can be incorporated with the emulsion. prior't'o coating- They rnay; however, be brought into contact therewith after coating. Thus a silver halide emulsion can ous solution. 10

I ing or in an overcoating in intimate contact with the emulsion layer. The compounds can be added ;to the emulsion or to adjacent coatings from aqueous solution or from an organic solvent, pref:- erably ethanol. Most of the compounds are sufficiently water-soluble to be utilized from aque- Other useful solvents include water-miscible solvents, e. g., ethanol, methanol, acetone, dioxane, etc., which can be mixed with water. The compounds may be added separately or simultaneously from separate solutions.

This invention is not limited to the use of gelatin as the binding agent for the silver halides. On the contrary, other hydrophilic colloids can be used. Suitable colloids include agaragar, polyglycuronic acids, zein, collodion, water-soluble cellulose derivatives, such as substantially hydrolyzed cellulose acetate, cellulose esters of hydroxy monocarboxylic acids, e. g., lactic or glycolic acids, alkali metal salts of cellulose esters of dicarboxylic acids, such as phthalic acid, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate and interpolymers thereof with unsaturated materials, such as styrene, maleic acid, etc., water'- soluble polyvinyl acetals and other hydrophilic synthetic or natural resins and polymeric compounds. Suitable hydrophilic colloids of the above types are described in United States Patents 2,110,491, 2,276,322, 2,276,323, 2,286,215, and 2,211,323.

The supports upon which the layers are coated may be paper, metal, cellulose derivative, superpolymers, e. g., nylon, etc., synthetic resins, e. g., polyvinyl chloride, etc. The pol'yglycols hereof may be added to the hydrophilic colloid silver halide emulsions over a wide range of proportions, e. g., from one part of polyglycol in 350,000 parts of emulsion to one part of polyglycol in parts of emulsion. The polyhydric alcohol or ether or ester thereof can be used in amounts from one part of such polyhydric alcohol compound to 12 to 170 parts of emulsion. The amount of sensitizing efiect obtained depends to some extent upon. the molecular weight of the particular compound or compounds employed and uponthe concentration which must be used. In general,- the higher the molecular Weight of the compound',the lower the concentration which must be used to give the optimum effect.

An advantage of this invention resides in the fact that the enhanced phototonic character (viz. state of sensitiveness to light). of photographic emulsions can be attained in a simple and economical manner. A further advantage is :that commercially available products are used. Another advantage is that the mixture of compounds may be used with' color formers, sensitizing dyes, fog inhibitors, etc., without having any deleterious effect thereon.

As many widely different embodiments of this invention can be made without departing from the spirit and scope thereof, it'is to be understood that the invention is not to be limited eX- cept as defined by the claims.

What is claimed'is:

LA photographic element comprising a support hearing at least one light-sensitive silver halide emulsion layer carriedthereby which has in contact with the silver'halide grains a poly. alkylene' glycol having a molecular weight oft-at least 400; the alkylene'groupsof. which contain 2 to 4 carbon atoms and constitute the only hydrocarbon groups in sa'id glycols and amember ether or ester radical.

2. A photographic element comprising a support bearing at least one light-sensitive silver halide emulsion layer carried thereby which has in contact with the silver halide grains a polyalkylene glycol having a. molecular weight of at least 400, the alklylene groups of which contain 2 to 4 carbon atoms and constitute the only hydrocarbon groups in said glycols and a saturated, aliphatic, polyhydric alcohol of 2 to 6 carbon atoms.

3. A photographic element comprising a support hearing at least one light-sensitive silver halide emulsion layer carried thereby which has in contact with the silver halide grains a polyalkylene glycol having a molecular weight 01' at least 400, the alkylene groups of which contain 2 to 4 carbon atoms and constitute the only hydrocarbon groups in said glycols and a glycol of 2 to 6 carbon atoms.

4. A photographic element comprising a support hearing at least one light-sensitive silver halide emulsion layer carried thereby which has in contact with the silver halide grains a polyalkylene glycol having a molecular weight of at least 400, the alkylene groups of which contain 2 to 4 carbon atoms and constitute the only hydrocarbon groups in said glycols and ethylene glycol.

5. A photographic element comprising a support hearing at least one light-sensitive silver halide emulsion layer carried thereby which contains a polyalkylene glycol having a molecular weight of at least 400, the alkylene groups of which contain 2 to 4 carbon atoms and constitute the only hydrocarbon groups in said glycols. and a member taken from the group consisting of saturated, aliphatic, polyhydric alcohols of 2 to 6 carbon atoms and their alkyl ethers and fatty acid esters containing not more than 3 carbon atoms in the ether or ester radical.

,6. A photographic element comprising a support hearing at least one light-sensitive hydrophilic colloid silver halide emulsion layer containin a polyethylene glycol having a molecular weight of at least 400 and wherein the ethylene radicals thereof constitute the only hydrocarbon groups of said glycol and a saturated, aliphatic, polyhydric alcohol 01' 2 to 6 carbon atoms.

'7. A photographic element comprising a support bearing at least one light-sensitive gelatin silver halide emulsion layer containing a polyethylene glycol having a molecular weight of at least 400 and wherein the ethylene radicals thereof constitute the only hydrocarbon groups of said glycol and a saturated, aliphatic, pol'yhydric alcohol of 2 to 6 carbon atoms.

8. A photographic element comprising a support bearing at least one light-sensitive gelatin silver halide emulsion layer containing a polyethylene glycol having a molecular weight of at least 400 and wherein the ethylene radicals thereof constitute the only hydrocarbon groups of said glycol and a glycol of 2 to 6 carbon atoms.

9. A photographic element comprising a sup port bearing at least one light-sensitive gelatinsilver halide emulsion layer containing a Polyethyleneglycol having a molecular weight of at.

least 400 and wherein the ethylene radicals thereof constitute the only hydrocarbon groups of said glycol and ethylene glycol.

Certificate of Correction Patent No. 2,441,389. May 11, 1948. RALPH KIN GSLEY BLAKE It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 1, line 29, for coloid read colloid; column 6, line 14, in the table, sixth column thereof, under the heading Gamma, for .27 read .72; lines 61 and 62,'in the table, sixth column thereof, under the heading Gamma, for the last three figures 3" d '32 4 91 real .91

column 9, line 11, for alklylene read allcg Zene; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 14th day of September, A. D. 1948.

THOMAS F. MURPHY,

Assistant Gammz'ssz'oner of Patents, 

